Before it is used in the fabrication of fuel elements, natural uranium is enriched in uranium 235 (the uranium 235 content going to 3% to 95%). An isotopic separation process is used to "enrich" the natural uranium in uranium 235. The physical and chemical processes used to produce enriched uranium also produce uranium with a uranium 235 content that is lower than the natural content: this is known as depleted uranium or Tails.

Ratio of the number of atoms of a given isotope of an element to the total number of atoms of that element contained in a material. It is expressed as a percentage.

TQM is a management tool to enhance quality, reduce costs and increase client satisfaction by reengineering traditional management methods.

Packaging specially designed to completely contain certain radioactive materials (spent fuel, vitrified waste, etc.) during transport and withstand possible accidents.

Treatment (or Reprocessing) of spent fuel to extract the fissile and fertile materials (uranium and plutonium) so as to allow their reuse, and to condition the various wastes in a form suitable for Storage and/or Disposal. The fission products and the transuranics are vitrified.